since moved to the National University of Singapore.">

By Steve Pointing 29/09/2015


NASA has delivered the first proof that moving ‘liquids’ on Mars’ surface are made of water, albeit extremely salty brines.
These are likely to be ten times saltier than seawater here on Earth and so a human would receive burns from contact with these brines.  However, extremely salty lakes that occur in many desert environments from California to Tibet do support simple microbial life that can tolerate high salt content – and so this new study suggests they may be the sort of extant life we could expect on Mars.  These microbes often colour the water vivid pink due to a pigment they contain called bacteriorhodopsin, and so I think that some scientists may now start wondering if this has potential as a ‘biosignature’ molecule for life on Mars. 

For many years NASA has had a ‘follow the water’ strategy to search for traces of life, since all life requires liquid water. The discovery of moving water on Mars really adds momentum to the search for life.  When water moves there is the opportunity for weathering of minerals and creation of nutrients to sustain life.  Any Martian microbes would also be able to use flowing brines to disperse and colonise new areas of Mars surface. 

There is however still a major problem that still faces any potential life in these brines and that is the inescapable radiation on Mars surface. Mars has high levels of ionising radiation because it only has a very thin atmosphere, unlike Earth’s thick atmosphere that shelters us and allows life to thrive.  The only real option on Mars is for life to avoid the radiation by colonising beneath a protective layer of rock in what is known as the ‘microbial cabana’ strategy.  Microbes can only do this in weathered rock, and flowing brines would certainly be a good weathering agent, so even if we do not discover little pink microbes in the brine itself, it adds to the possibility of finding other photosynthetic green microbes that form the microbial cabana in Mars-like environments on Earth such as the Dry Valleys of Antarctica. 

Read more on this story (abstracts only without a subscription) 

Flowing water on Mars surface (Nature Geoscience): http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2546.html 

The microbial cabana hypothesis (Nature Reviews Microbiology): http://www.nature.com/nrmicro/journal/v10/n8/full/nrmicro2831.html 

The image shows moving ‘rivers’ of brine on Mars surface (credit: NASA JPL)